Nanocrystalline phosphor and coated nanocrystalline phosphor as well as method of preparing coated nanocrystalline phosphor

Abstract

Provided is a nanocrystalline phosphor having a core/shell structure formed by a core of a group 13 nitride semiconductor and a shell layer, covering the core, including a shell film of a group 13 nitride mixed crystal semiconductor. This nanocrystalline phosphor has high luminous efficiency, and is excellent in reliability. Also provided is a coated nanocrystalline phosphor prepared by bonding modified organic molecules to the nanocrystalline phosphor and/or coating the nanocrystalline phosphor with the modified organic molecules. This coated nanocrystalline phosphor has high dispersibility. Further provided is a method of preparing a coated nanocrystalline phosphor by heating a mixed solution containing a core of a group 13 nitride semiconductor, a nitrogen-containing compound, a group 13 element-containing compound and modified organic molecules.

1. A coated nanocrystalline phosphor, comprising:
 a nanocrystalline phosphor having a core/shell structure, said nanocrystalline phosphor including
 a core of a group 13 nitride semiconductor; and 
 a shell layer, covering said core, including a shell film of a group 13 nitride mixed crystal semiconductor; and 
 
 modified organic molecules bonded to and/or coating an outer surface of the nanocrystalline phosphor, wherein 
 said shell layer is formed by:
 a first shell film of a group 13 nitride mixed crystal semiconductor having a smaller band gap than said core and covering said core; and 
 a second shell film having a larger band gap than said core and coating said first shell film. 
 
 
     
     
       2. The coated nanocrystalline phosphor according to  claim 1 , wherein
 nitrogen atoms of said core and group 13 atoms of said shell layer are chemically bonded to each other, and 
 nitrogen atoms of said shell layer and group 13 atoms of said core are chemically bonded to each other. 
 
     
     
       3. The coated nanocrystalline phosphor according to  claim 1 , wherein
 said core is made of gallium nitride. 
 
     
     
       4. The coated nanocrystalline phosphor according to  claim 1 , wherein
 said group 13 nitride mixed crystal semiconductor contains 5 to 60 mole % of indium atoms. 
 
     
     
       5. The coated nanocrystalline phosphor according to  claim 1 , wherein the thickness of said shell layer is not more than twice the Bohr radius. 
     
     
       6. The coated nanocrystalline phosphor according to  claim 1 , wherein said shell layer has a multilayer structure formed by a plurality of shell films. 
     
     
       7. A method of preparing a coated nanocrystalline phosphor according to  claim 1  by mixing modified organic molecules into a mixed solution containing a core of a group 13 nitride semiconductor, a nitrogen-containing compound and a group 13 element-containing compound. 
     
     
       8. The method of preparing a coated nanocrystalline phosphor according to  claim 7 , wherein
 at least either said group 13 element-containing compound or said nitrogen-containing compound is a compound having bonds of indium and/or gallium and nitrogen. 
 
     
     
       9. The method of preparing a coated nanocrystalline phosphor according to  claim 7 , wherein
 a solvent for said mixed solution is a hydrocarbon-based solvent. 
 
     
     
       10. The method of preparing a coated nanocrystalline phosphor according to  claim 7 , wherein
 the temperature for heating said mixed solution is 180 to 500° C. 
 
     
     
       11. The method of preparing a coated nanocrystalline phosphor according to  claim 7 , wherein
 at least two types of said modified organic molecules are employed.